package principle.facade;

/**
 * @author malguy-wang sir
 * @create ---
 */
public class screen {//屏幕
    //单例模式-饿汉式
    private static screen instance = new screen();
    public static screen getInstance() { return instance; }
    public void up(){ System.out.println("screen on"); }
    public void down(){ System.out.println("screen down"); }
}
